1. Field of the Invention
The present invention relates generally to an arrangement of fiber optic cables that are utilized for transmitting signals in a telecommunications network. More particularly, the present invention relates to reducing the slack and routing complexity that normally result when equipment is coupled using the cables.
2. Background of the Invention
Currently, signals transmitted from a central office to a subscriber in a telecommunications network undergo several transformations. The signals are transmitted from the central office as optical signals that travel along fiber optic cables. The optical signals are received at a CEV (xe2x80x9ccontrolled environment vaultxe2x80x9d) where they are converted to electrical signals that are transmitted over copper wires and then are converted back to optical signals before being transmitted to the subscriber.
FIG. 1 is a schematic diagram of a conventional CEV 103 within a telecommunications system. CEVs house electronic equipment that converts the signals and are typically located about ten (10) to twelve (12) feet deep underground. The signals are temporarily converted to electrical signals for the purpose of amplifying or otherwise adjusting them. Typically, fiber optic cables 101 enter the CEV from a central office 100 and connect to multiplexers 102. Multiplexers 102 convert the optical signals into electrical signals. Jumper cables 106 are wired from multiplexers 102 to an equipment bay assembly shelf 112, within an equipment bay assembly 113, which provides electrical signal cross-connects and separates the respective signals into a dial tone. Fiber optic cables 108 connect the equipment bay assembly shelf 112 to a fiber termination shelf 114. The fiber termination shelf 114 is a cross-connect, and ultimately connects the fiber optic cables to subscribers 116. A ladder, pump, and battery supply (not enumerated in FIG. 1) are also contained in the CEV.
FIG. 2 is a schematic diagram illustrating a typical configuration of an equipment bay assembly 113. An example of an equipment bay assembly system is the DISC*S MX Bay Assembly manufactured by Marconi Corporation PLC. Fiber optic cables 205 are coupled to a fiber distribution shelf, MDS #1204, from common shelf 112. There are twenty-eight (28) T-1 lines coupled to the common shelf 112, carrying twenty-four (24) telephone lines between the common shelf and MDS #1. Although not shown in the present embodiment, fiber optic cables may also be connected to MDS #2206.
FIG. 3 is a depiction of a fiber distribution shelf 204 illustrating how fiber optic cables 205 are attached. Fiber distribution shelf 204 has fourteen (14) removable cards (not all shown) 304a-304n each having four (4) fiber ports. Cards 304 fit into slots (not shown) in a housing of fiber distribution shelf 204. The fiber ports are color-coded and numbered according to a well-known universal color code. (according to this color code, blue is xe2x80x9c1xe2x80x9d, orange is xe2x80x9c2xe2x80x9d, green is xe2x80x9c3xe2x80x9d and brown is xe2x80x9c4xe2x80x9d). Fiber cables 205 are quad jumper cables, such that each cable consists of four (4) separate cables that are grouped together. Therefore for each card, the cable has four (4) ends, one of each color, grouped together to form a single cable.
As shown in FIG. 4, each of the 14 fiber optic cables 205 are then connected from one of the cards in the fiber distribution shelf 204 to fiber termination shelf LGX 402. From fiber termination shelf 402, signals are ultimately transmitted to a neighborhood to supply service to respective subscribers.
The conventional configuration of fiber optic cables within a CEV as described above is associated with several difficulties and inefficiencies. Particularly, while each card 304 can accommodate 4 fiber optic cables, each handling 24 telephone lines for a total of 1344 lines in fiber distribution shelf 204, common shelf 112 can only accommodate 28 T-1 cables, or 672 telephone lines. As a result, only two (2) of the four (4) available ports in each card are used. Although equipment bay assemblies, such as future releases of the MX system may use a second fiber distribution shelf (MDS # 2, shown as 206 in FIG. 2), it cannot concurrently be used to connect to the fiber termination shelf 402. As shown in FIG. 5, the unused cables are instead loosely hanging by the equipment bay assembly. Since all of the cables are the same length, there is slack 500, which sometimes causes damage to the cables.
FIGS. 6a and 6b illustrate conventional means for handling slack in fiber optic cables 602 that couple the fiber distribution shelf 204 to the fiber termination shelf 402. As shown in FIG. 6a, a fiber management device 600 is placed on top of equipment bay assembly 113, and excess cable 602 is contained within the device 600. However, device 600 is expensive, and it also is not specifically tailored to particular equipment bay assemblies. Depending on the length of the excess cable, it may be difficult to install the device 600.
FIG. 6b depicts an arrangement of cables connecting the fiber distribution shelf to the fiber termination shelf that are looped in order to reduce the amount of excess cable that is hanging loosely. As shown, the excess cable 602 is simply looped and placed aside. Because the space in which the cables are looped is narrow, the looping can cause sharp bends 604. Such sharp bends may damage or break fiber optic cables, or otherwise affect the transmission characteristics of the cables, necessitating their replacement.
FIG. 7 illustrates a conventional connection of quad jumpers 205 to fiber distribution shelf 204. Because the ends of the cables are all the same length and there is a separate cable for each group of four (4) jacks on each card, it is difficult to efficiently wire the ends of the cables into the ports in the cards 304 of the fiber distribution shelf 204 to reduce slack. Moreover, there are no indicator labels on the cable ends to assist one installing the cables. In addition, there is a separate cable for each group of four (4) jacks on each card.
As can be seen, conventional cable wiring or routing paradigms lead to a mass of cables for which slack is not efficiently removed. As a result, cables frequently obstruct passage in the close confines of the CEVs or are susceptible to damage or breakage.
The present invention solves at least the foregoing problems in the art by providing a cost-effective device, system, and method for managing slack in fiber optic cables. The slack management technique of the present invention is more cost effective and provides more protection for the cable than in conventional systems.
In the present invention, individual fiber optic cables are bundled together and placed in a sheath. The ends of the individual fiber optic cables extend past the sheath and are staggered on one end to correspond to ports on a shelf on an equipment bay assembly while on the other end, the cables are the same length to accommodate a variety of fiber termination shelves.